Green Tortoise is 1/2 block from pikes place market and a good location to walk to many other things including the waterfront, belltown & pioneer square nightlife, etc.

Freeways and Roads - here is a LINK for the states transportation site, which will tell you all you need to know about the roads, ferries, etc. you can find the ferry schedule and prices here, traffic cameras, approximate travel time needed between places, etc.

Toll roads/bridges - as of april 2013 the I-90 bridge which goes from South Seattle to South Bellevue and is the only road access for Mercer Island is free to drive on. However connecting the north sides of the 2 cities is the "520 floating bridge" which has $3-5 toll to cross, depending on time of day(but its a cool view). They send you a bill by mail after they photograph your plate. The "Narrows Bridge" in Tacoma charges about $5 but just in the eastbound direction and there is a booth to pay, westbound is free. Currently the only other "pay as you go" roads are on hwy 167 but only if you use the carpool lane.

Thanks so much for the info and intro. I particularly love the we've site you provided for housing that bnb site :) my tkts are booked, plans are not solid! Super duper excited!! Holler any time too! Look forward to sharing my experience.-Aries